Do型： Leave me alone! Get out! Sit down,please. Wake up. Stand up. Open the door now. Do it now. Be型： Be quiet! Be nice. Be a good boy. Don't be so mean. Don't be late. Let型： Let's go. Let's dance. Let me help you. Let's begin the lesson. 例子太多了,记住祈使句都是动词原形开头.否定式是don't +动词原形
